Development of sulfonated poly(ether ether ketone)/polyethersulfone ‐ crosslinked quaternary ammonium poly(ether ether ketone) bipolar membrane electrolyte via hot‐press approach for hydrogen/oxygen fuel cell

Hot-pressing is a simple and promising technique for the integration of a proton exchange membrane (PEM) and anion exchange membrane (AEM) to allow both positive and negative ions simultaneously in a bipolar membrane (BPM). In this research, a composite sulfonated poly(ether ether ketone)/polyethersulfone (sPEEK/PES) was prepared as a PEM electrolyte, and ionic-crosslinked quaternary ammonium poly(ether ether ketone) (cQAPEEK) was prepared as an AEM electrolyte. The central composite design (CCD) of response surface methodology (RSM) was adopted as an experimental plan. This method is used to develop a mathematical model to analyze the effect of hot-press conditions on adhesion and properties of sPEEK/PES-cQAPEEK BPM and ultimately to obtain optimum operating pressure and temperature. The temperature and gauge pressure are set as input parameters, and the ionic conductivity of the membrane is considered to be the response under investigation. The optimum temperature and gauge pressure of the hot-press conditions for the development of the sPEEK/PES-cQAPEEK BPM were found to be 120°C and 3 tonnes/square inch, respectively. This result was confirmed by a scanning electron microscopy (SEM) analysis, where good and fit electrolyte layer adhesion contact was visualized, leading to better ion transport across the electrolyte. SPEEK/PES-cQAPEEK BPM has a peak power density of 51.51 mW cm−2 which is comparable to that of Nafion 117-cQAPEEK BPM (100.17 mW cm−2). This result suggests that the sPEEK/PES-cQAPEEK BPM had the ability to be used as an electrolyte for BPMFC applications by considering the optimum hot-press conditions.